Multiple electrode spark gaps with a condenser connected in parallel with one spark gap



A. BRUGNQLA MULTIPLE ELECTRODE SPARK GAPS WITH A CONDENSER CONNECTED IN PARALLEL WITH ONE SPARK GAP Filed July 20, 1964 I IHUJLT 2 Sheets-Sheet .1

H TTOR/VE) June 6, 1967 A. BRUGNOLA 3,324,347

MULTIPLE ELECTRODE SPARK GAPS WITH A CONDENSER CONNECTED IN PARALLEL WITH ONE SPARK GAP Filed July 20, 1964 2 Sheets-Sheet 2 INVENTOR: ANTHONY BRUGNOLA,

751. A WQ r roe/v5 y United States Patent 3,324,347 MULTIPLE ELECTRGDE SPARK GAPS WITH A CONDENSER CGNNECTED IN PARALLEL WITH ONE SPARK GAP Anthony Brugnola, 2012 th St, Palmetto, Fla. 33561 File-d July 20, 1954, Ser. No. 383,758 3 Ciaims. (Cl. 315-59) This invention relates to devices for igniting air-fuel mixtures disposed in a state of compression within the combustion chamber of internal combustion engines, and more particularly to spark plugs for vehicular and especially automobile engines, and the like.

Modern engines with their higher compression ratios, shorter piston travel and faster rotary speeds impose a host of problems on the construction and operation of spark plugs; requirements frequently conflict with one another, and the solution of one problem is often achieved but by an inadequate response to another.

Thus, the area of the spark plug opening or port should be kept to a minimum so that as large as possible an area is available for the intake and exhaust valves to promote optimum breathing of the engine. The spark plug port should be located as close as possible to the exhaust valve, as this enhances the combustion sequence. Within the combustion chamber of an engine, the air-fuel mixture ignites at about 650 F., but temperatures in the vicinity of the exhaust valve, at high speeds under heavy load, often reach 1700 F. This heat is dispersed in part by the washer inserted between the spark plug body and its port. However, the insulator must be made of such material and should be so designed as to be capable of radiating most of this heat away lest it build up along the electrode tip extending into the chamber and cause the electrode to incandesce and induce pre-iguition.

Another problem is caused by the compression within the chamber which may attain 180 lbs. per square inch. The potential at the electrode tip must be able to ionize a path for a spark to be discharged through this highly compressed volume of air-fuel mixture. As this air-fuel mixture is also in a state of violet turbulence around the electrode tip, the volume of the mixture exposed to the ionizing potential is materally enlarged. The chamber is designed to promote the turbulence by contouring a squish section within it, so that when the mixture is ignited a uniform, evenly propagating flame front will be initiated.

At lower speeds, spark plugs are fouled by the buildup of carbon, caked oil and additives to the fuel intended to prevent knock. These deposits on insulator and electrode tip are responsible for current leakage so that when the ignition field collapses and a spark should be discharged, the potential available is insufiicient for ionizing the fuel-air mixture in the gap; no ignition therefore occurs.

It is a primary object of this invention to deal with the multiple problems exemplified above, and to provide an ignition device or spark plug which will eliminate the drawbacks of igniters or spark plugs heretofore available and will respond to the requirements of the most advanced modern engines.

It is another important object of the present invention to provide an ignition or spark plug capable of igniting a larger volume of the air-fuel mixture than was heretofore possible, and to do so safely and reliably whereby to promote even and effective combustion.

A further object of the invention is the provision of a spark plug which is not fouled by the accumulation of carbon and other deposits deriving from combustion.

Ancilliary objects of the invention are spark plugs which can be manufactured readily and economically, are of greatly improved efficiency and operating life, and lend Patented June 6, 1967 themselves to ready application to any existing engine port so as to replace any particular spark plug specified for said engine.

Other objects, and the manner in which the same are attained, will become apparent as this specification proceeds.

The present invention contemplates, broadly, an igniter or spark plug which incorporates, disposed within or outside the ins-ulator, a plurality of capacitors, each of predetermined capacitance and provided with an independent electrode which projects separately and at a distance from any adjacent electrode or electrodes, into the combustion chamber. When the ignition field collapses through action of the breaker points, a number of sparks will be discharged simultaneously between the main electrode, the individual electrodes connected to the capacitors, and the ground electrode. The total length of these sparks is equal to the sum of the distances between electrodes; it may be as much as of an inch, or more. This is about ten times the width of a spark gap in present day spark plugs. Extension of the overall spark length to a different order of magnitude is responsible for exposing a much greater volume of air-fuel mixture to the igniting temperature, initiating a huge and continuous flame front and propagating it through the chamber, and correspondingly increasing the amount of useful work performed.

Seen in its more specific aspects, the invention embraces a separate chamber within the spark plug but communicating with the main combustion chamber, whereby a materially enlarged area is made available for extra electrodes connected to capacitors. The electrodes are provided in the form of flat strips rather than as the usual rod type, whereby the area of each available to the potential and for spark discharge, is materially increased. These extended areas will have a vastly reduced tendency to foul; however, the invention contemplates the use of a high silica glass or a vitro-ceramic material such as Pyroceram for the insulator which is apt to reduce fouling substantially to the vanishing point while simultaneously, having greatly improved heat radiating characteristics.

In the drawing accompanying this specification and forming part thereof, a preferred embodiment of the invention is illustrated diagrammatically by way of example, and with no limitative intent.

In the drawings:

FIG. 1 is a side view, partly in section, of a spark plug according to the invention;

FIG. 2 is a cross-section through the spark plug of FIG. 1 taken along line 11-11;

FIG. 3 is a bottom view of the auxiliary chamber which is a detail of FIGS. 1 and 2.

Referring to the several figures of the drawing wherein like elements are denoted by identical reference numerals, and first to FIGS. 1 to 3, inclusive, the preferred embodiment of the invention shown in these figures involves a spark plug containing one main electrode as well as two auxiliary electrodes provided with capacitors.

This spark plug comprises an insulator body 1 which may take many forms, but in this case is in the shape of a slab, widening toward its free end, with several fins 2 on both the wider faces, at waist 3 in its middle which allows a split seal 4 to fit its upper shoulder, and a seal 5, also in two halves, to fit its lower shoulder. Force fitted between the two seals 4 and 5, which are of ductile material, is a split collet 6 with a threaded outer face 7. Screwed into this collet is a cupped shell 10 which is the single support for the spark plug and forms a hexagonal nut 9 to allow a wrench to screw the spark plug into its port. This shell 10 is so designed that the base of the insulator body is seated tightly therein, another seal 8 being squeezed between the base and shell 10. Steel shell 10 carries a threaded section that fits the engine port and forms a channel 11 leading to a concavity or auxiliary chamber 13 formed by shoulder 12 of shell 10 and the base of the insulator body.

FIG. 2 shows the same spark plug turned 90 degrees on its vertical axis. Its upper part comprises a main electrode stem 14 secured within the insulator body 1, and threaded into a connecting nut 15 to which the cable leading from the distributor of the engine can be attached. Mounted on stem 14 is main electrode 16 which, although smaller, follows the general outline of insulator body 1 and terminates at the bottom in an electrode strip 17, which projects from the insulator body 1 into chamber 13. Parallel to the plate-shaped main electrode 15, and separated from it by dielectric material, preferably ruby mica in a sheet of about 10 to 12 mils, is a thin plate 18' connected to another plate 18" of the same shape, together with which, and with layers of dielectric disposed between the two plates 18' and 18", it forms a first, U- shaped capacitor 18. A similar capacitor 19 of inverted U-shape has one plate, 19', extending into the U formed by capacitor 18, being separated from plate 18' and 18" by layers of dielectric, such as mica, while another plate 19", extends on the outside of the U formed by capacitor 18, and is separated from plate 18" by another layer of dielectric. Capacitor 18 ends in an electrode strip 20 which projects beyond insulator body 1, and, similarly, capacitor 19 has an independent electrode ending in a metal strip 21. As the seal 8 disposed between the insulator base and steel shell 10, has a tab 22 projecting beyond the shell 10 but remains in contact with it throughout its periphery, it forms a ground electrode 22.

Thus, as shown in FIG. 3, three gaps are formed within the chamber 13, namely the gaps between main electrode 17 and capacitor electrode 20, capacitor elec trode 20 and capacitor electrode 21, and capacitor electrode 21 and ground 22, respectively.

Insulator 1 may be made of alumina or beryllia ceramic, or a vitro-ceramic such as Pyroceram, or borosilicate glass or high-silica glass. Alumina ceramic is now commonly used in spark plugs, because of its ability to resist heat shock and retain its dielectric qualities at elevated temperatures. Beryllia ceramic is somewhat superior to alumina ceramic in some physical characteristics and is used in severe applications. Vitro-ceramics are a family of materials that from their glassy state have been converted into crystalline ceramics by heat and the use of nucleating agents. They are extremely hard, heat shock resistant, and have favorable electrical properties at elevated temperatures. Being non-porous and distinguished by an extremely hard, smooth and glossy surface, they are particularly resistant to being coated by carbon, caked oil, fuel additives, etc. Their thermal conductivity, however, is low, and it is necessary to use fluted fins to dissipate the heat. High silica glass (up to 95% silica) and borosilicate glass are also materials that satisfy the requirements for spark plug insulator bodies, but they are more expensive and harder to fabricate. Vitro-ceramics have the advantage of being available in various coefficients of expansion: from positive to zero to negative. This is highly desirable when metal shells and inserts are considered.

Many materials are available for the electrode-capacitors units. In general, good conductors like copper, are preferable, except for the electrode tips which may be alloys, like nickel-cadmium, or other materials like platinum. The plates of the capacitors themselves are thin foils of copper or aluminum or other conducting material separated by layers of dielectric material such as mica. Here, practical considerations dictate the use of dielectric layers with high resistance to voltage puncture. In most ignition systems, especially of the transistorized variety, very high voltages are developed, which at times may reach 45,000 volts. At the same time, the capacitance of a capacitor is inversely proportional to the thickness of the insulating layers. For the design of capacitors, a formula can be used.

wherein A is the plate area, K is the dielectric constant, d is the clearance between plates, and It stands for the number of plates. Values for resistance to voltage puncture are 410 volts per mil of thickness for quartz, 350 volts per mil for pyrex glass and vitro-ceramics, volts per mil for alumina ceramic, and 3,600 to 5,600 volts per mil for ruby mica. Values for the dielectric constant are 3.8 for quartz, 4.8 for glass of the pyrex variety, and vitro-ceramics, about 5 for alumina ceramics, and 5.4 for ruby mica. From these values, it can be deduced that ruby mica is by far the best material to use for insulating the plates of the capacitors. As shown in FIG. 2, the main electrode plate 16 and capacitors 18 and 19 are used in an alternate plate arrangement, thus forming two separate capacitors. An example of their value might be: total area of each plate: 1 sq. inch, number of plates, each face being a plate of a capacitor, 4, dielectric constant of insulator, ruby mica 10 mil thick, 5.4, clear distance between plates: .01. Value of capacitor in micromicro farads equals 360, which is a high capacitance and quite suitable, but it can be cut down or doubled or tripled without practical difliculties.

The modus operandi of a spark plug built according to the present invention follows electrical principles: from a generating source and through the use of a coil, a potential of several thousand volts is established in the spark plugs main electrode 16, which is directly connected by a line to a distributor unit. When the breaker in this unit cuts off the potential, the field around the coil collapses, and a spark will be discharged along an ionized path from the tip 17 of this electrode to the tip 20 next to it, which will then temporarily charge its capacitor 18 and then discharge from its tip 20 a spark to the tip 21 of the next capacitor electrode 19 and so on to the ground electrode 22. Although the discharged total spark will be the sum of the lengths of each spark, the discharge can be considered virtually simultaneous.

It is also possible to connect the two capacitors, or several of them, in parallel with the main electrode and obtain the same length and ignition heat of each single spark in an extended form. In either case, the ignition so initiated will be over a much larger volume of air-fuel mixture, and combustion will be improved correspondingly.

I wish it to be understood that I do not desire to be limited to the details of construction, design and operation shown and described, as modifications within the scope of the following claims which will involve no departure from the spirit of the invention, nor any sacrifice of the advantages thereof, may occur to workers in this field.

I claim:

1. A spark plug comprising in combination, an insulator body, a main electrode and a ground electrode associated with said insulator body, a plurality of auxiliary electrodes interposed in spaced relationship between said main electrode and said ground electrode, and a capacitor connected with each of said auxiliary electrodes, said capacitors comprising a U-shaped plate structure and an inverted U-shaped plate structure, said plate structures mutually engaging one another, and sheets of dielectric interposed between said main electrode and the adjacent capacitor, and between the plates of capacitors thus mutually engaged.

2. A spark plug comprising in combination, an insulator body, a main electrode and a ground electrode associated with said insulator body, a plurality of auxiliary electrodes interposed in spaced relationship between said main electrode and said ground electrodes, and a capacitor connected with each of said auxiliary electrodes, said main electrode and said auxiliary electrodes being mounted on fiat strips traversing parallel to one another, said insulator body, said capacitors comprising a U- shaped plate structure and an inverted U-shaped plate structure, said plate structures mutually engaging one another, and sheets of dielectric interposed between said main electrode and the adjacent capacitor, and between the plates of capacitors thus mutually engaged.

3. A spark plug comprising in combination, an insulator body, a main electrode and a ground electrode associated with said insulator body, a plurality of auxiliary electrodes interposed in spaced relationship between said main electrode and said ground electrode, and a capacitor connected with each of said electrodes, said main electrode and said auxiliary electrodes being provided as flat strips traversing parallel to one another, said insulator body comprising a recessed base defining an auxiliary combustion chamber, said electrodes including tips projecting into said auxiliary combustion chamber, said capacitors comprising a U-shaped plate structure and an inverted U-shaped plate structure, said plate structures mutually engaging one another, and sheets of dielectric interposed between said main electrode and the adjacent capacitor, and between the plates of capacitors thus mutually engaged.

References Cited UNITED STATES PATENTS 1,311,261 7/1919 Braselton 313123 X 1,941,279 12/1933 Sharpnack 313143 2,260,399 10/1941 Peters 313123 2,262,769 11/1941 King 313-123 X 2,334,203 11/1943 King 313123 2,483,357 9/1949 Winholm 313123 X JAMES W. LAWRENCE, Primary Examiner. C. R. CAMPBELL, Assistant Examiner. 

1. A SPARK PLUG COMPRISING IN COMBINATION, AN INSULATOR BODY, A MAIN ELECTRODE AND A GROUND ELECTRODE ASSOCIATED WITH SAID INSULATOR BODY, A PLURALITY OF AUXILIARY ELECTRODES INTERPOSED IN SPACED RELATIONSHIP BETWEEN SAID MAIN ELECTRODE AND SAID GROUND ELECTRODE, AND A CAPACITOR CONNECTED WITH EACH OF SAID AUXILIARY ELECTRODES, SAID CAPACITORS COMPRISING A U-SHAPED PLATE STRUCTURE AND AN INVERTED U-SHAPED PLATE STRUCTURE, SAID PLATE STRUCTURES MUTUALLY ENGAGING ONE ANOTHER, AND SHEETS OF DIELECTRIC INTERPOSED BETWEEN SAID MAIN ELECTRODE AND THE ADJACENT CAPACITOR, AND BETWEEN THE PLATES OF CAPACITORS THUS MUTUALLY ENGAGED. 